linux-kernel - Re: [PATCH v8 0/6] kvm: level irqfd support

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20120816125337.GA21526@redhat.com>
Date:	Thu, 16 Aug 2012 15:53:37 +0300
From:	"Michael S. Tsirkin" <mst@...hat.com>
To:	Alex Williamson <alex.williamson@...hat.com>
Cc:	avi@...hat.com, gleb@...hat.com, kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v8 0/6] kvm: level irqfd support

On Thu, Aug 16, 2012 at 06:34:52AM -0600, Alex Williamson wrote:
> > > > So I'm inclined to say source IDs are a requirement for shared
> > > > interrupts.
> > > 
> > > Can yo show a specific example that breaks?
> > > I don't think it can exist.
> > 
> > Only the edge vs level interaction if we define the policy above for
> > de-assert.
> 
> Hmm, there is still a race w/ level.  If we have a number of
> level-deassert-irqfds making use of the same gsi and sourceid and we
> individually de-assert and notify, a re-assert could get lost if it
> happens before all of the de-asserts have finished.
> We either need
> separate sourceids or we need to do a single de-assert followed by
> multiple notifies.  Right?  Thanks,
> 
> Alex

Good catch, I agree, we need a single deassert.

I think I see how to implement this without reference counting and
stuff.  So we chain all auto-deassert irqfds for a given GSI together,
and have a single ack notifier.  When list becomes empty, remove the ack
notifier.

It's actually a good thing to do anyway, too many ack notifiers
would slow unrelated GSIs down.

-- 
MST
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/